The present invention relates to a fuel supply control system for controlling the amount of fuel supplied to an internal combustion engine, and more particularly to a fuel supply control system in which a fuel supply control means is driven by a step motor.
Fuel supply control means such as throttle valves in spark ignition engines and control levers in diesel engines have conventionally been driven by a step motor which is energized to a step position corresponding to a position to which an accelerator pedal is depressed for thereby effecting fuel supply control.
Prior fuel supply systems have been disadvantageous in that the torque generated by the step motor varies due to variations in a power supply voltage applied to a step motor exciting circuit, so that the step motor tends to fail to produce a torque necessary for actuating the fuel supply control means, resulting in a step-out. One solution has been to use a feedback potentiometer, for example, for detecting the position of the step motor rotor to achieve increased operation reliability.